This invention relates to a disposable wipe-out sheet suitable for wiping out dust and/or dirt from floor or wall surfaces.
Japanese Patent Application Publication No. 1997-135798 describes a disposable wipe-out sheet comprising a heat-sealable synthetic resin base sheet and a plurality of heat-sealable filaments bonded to the base sheet and extending in one direction. These filaments are obtained by deregistering or opening a tow of continuous filaments and bonded to the base sheet by a plurality of sealing lines extending transversely of the filaments and arranged intermittently in the one direction. An assembly of these filaments obtained by deregistering the tow is bulky and, along the sealing lines formed by locally pressing this assembly under heating, a plurality of filaments are molten and solidified to form a high density film bonded to the base sheet. Between each pair of the adjacent sealing lines, filaments form convex bridge-like portions describing arcs which are convex upward from the base sheet.
One of measures to improve a productivity per unit time of the wipe-out sheet of prior art is to feed the heat-sealable synthetic resin base sheet and the filaments at a high velocity onto a production line so that the base sheet and filaments may be heat-sealed together at a high velocity corresponding to said high feeding velocity. To improve the heat-sealing velocity, it is preferable to use synthetic resin having a relatively low melting point for both the base sheet and the filaments and to use the press having high temperature and pressure. However, if a temperature of the press is adjusted to a level substantially higher than the melting point of the synthetic resin, both the base sheet and the filaments would be deformed due to heat transferred from the press in their regions other than their regions in which the sheet and the filaments. As a result, it is difficult for the wipe-out sheet to maintain its initial shape. Accordingly, an improvement of the productivity by adopting a higher press temperature is inevitably limited.
It is an object of this invention to design a disposable wipe-out sheet so that a relatively high press temperature can be employed during a process for making the wipe-out sheet.
According to the invention, there is provided a disposable wipe-out sheet comprising a heat-sealable synthetic resin base sheet and a plurality of heat-sealable synthetic resin long fibers heat-sealed with the base sheet and extending in one direction, wherein the long fibers are heat-sealed with the base sheet by a plurality of sealing lines arranged intermittently in the one direction, wherein: the long fibers comprise core-sheath type conjugated fibers wherein a melting point of the sheath is lower than a melting point of the core and such difference of the melting points is at least by 30xc2x0 C.
According to the invention, there is also provided a process for making a disposable wipe-out sheet comprising a heat-sealable synthetic resin base sheet and a plurality of heat-sealable synthetic resin long fibers heat-sealed with the base sheet and extending in one direction, wherein said long fibers are heat-sealed with the base sheet by a plurality of sealing lines arranged intermittently in the one direction, wherein:
the long fibers comprise core-sheath type conjugated wherein a melting point of the sheath is lower than a melting point of the core and such difference of the melting points is at least by 30xc2x0 C.; a difference between a melting point of the base sheet as measured along the sealing lines and a melting point of the sheath in the conjugated fiber is less than 20xc2x0 C.; and the base sheet and the long fibers are bonded together at a temperature higher than the melting point of the sheath in the conjugated fiber by 20xc2x0 C. or more but lower than the melting point of the core in the conjugated fiber.